A transparent plastic material has advantages of being light and resistant to shattering. Thus, it has been considered as an alternative to a known glass in the optical lens industry, flat panel display or the like. In particular, more recent demands for a portable display have increased according to the development of mobile communications, and the next-generation rollable display has been realized. Therefore, the concerns for transparent plastic material have been doubled. However, most of plastic materials have soft surface, so that their surface strength and wear resistance are bad. Therefore, there is a problem that they are easily scratched. In addition, plastic materials have unsatisfactory barrier properties to various gases including oxygen. Thus, there is a limitation in their application to most of flat panel display based on organic materials.
In order to overcome the limitations of plastic materials, a protecting film is generally formed on the surface of plastic material by using an organic, inorganic, or organic-inorganic complex as a coating agent, and used. Specifically, a silicone-based coating agent has been recently considered because of its excellent light transmittance, reproductive property or the like. In addition, since silicone is ubiquitous or unharmful to environment and human to be recognized as an environment-friendly material, it has been noted as an alternative candidate for other organic polymer and metal coating agents.
However, since the silicone-based coating agent is provided for a plastic substrate, there is a limitation that all of the coating and application process should be performed at low temperature, which is lower than a glass transition temperature allowed by the substrate material. Accordingly, most of high strength silicone coating process has required expensive equipments such as sputtering, vacuum evaporation, ion deposition, and PECVD (plasma enhanced chemical vapor deposition). However, in the case of using such physical/chemical application method, there are problems that the reduction in profit is caused due to the expensive equipments, and the process should be performed for a long period of time to obtain a coating with a predetermined thickness, thereby resulting in a limitation of productivity.
On the contrary, a conventional liquid coating method using a silicone-based polymer such as spin coating, dip coating, roll coating, and spray coating has apparent advantages with respect to basic equipments or processing time. However, the silicone coating by the liquid application slowly hardens at low temperature, and upon hardening it for a long period of time, the hardening reaction does not sufficiently occur not to achieve sufficient mechanical properties such as membrane strength, and wear resistance, barrier property or the like. In order to facilitate the reaction of siloxane polymer, a method for improving reactivity by using a coating composition containing an acid, a base, an ammonium salt or the like has been generally known. However, in the case of using an acid catalyst and ammonium salt, the improved properties are not sufficiently obtained. In the case of using a base catalyst such as aqueous ammonia and organic amine that facilitates condensation of silicone-based resin, there is a problem that the storage of coating composition itself is reduced, so that it cannot be substantially applied to the process.
In the conventional technologies, a specific method for achieving low temperature hardening, a problem-free process, and improving the mechanical properties of substrate, barrier property or the like by using a base catalyst such as aqueous ammonia and organic amine has not been yet disclosed. Accordingly, a method for improving strength of substrate, wear resistance, barrier property or the like under the process condition of low temperature is greatly needed.